This trial will attempt to define the role of rhu GM-CSF as an immunomodulator of neonatal bone marrow myeloid progenitor activity, its influence on circulating peripheral neutrophil counts and their functional activity, and whether this results in the prevention of neonatal nosocomial infection. Any significant reduction in the incidence, morbidity and mortality of neonatal nosocomial infection will greatly reduce the number of hospital days required for preterm newborns and reduce the amount of intensive care support associated with this disorder.